In 3GPP (3rd Generation Partnership Project) which is a project aiming to standardize a mobile communication system, the introduction of a Device to Device (D2D) service is discussed as a new function in Release 12 and later (see Non Patent Document 1). The D2D service (D2D ProSe) includes the discovery of a proximal terminal (Discovery) and device-to-device communication (Communication).
Here, a D2D radio resource (resource pool) that is used in a D2D service and is decided beforehand within a cell is used in the D2D service within the same cell (an Intra-cell D2D service).
On the other hand, in order to perform a D2D service between different cells (an Inter-cell D2D service), synchronization between different cells and sharing of the D2D radio resources are necessary.